When a person is being sly about what they are up to with the opposite sex. Not telling anyone about who they are contacting/seeing.

Snake Derick signs;
-Fake excuses why they can't come out.
-Hiding text messages from others.
-Shifty eyes and cheeky grin when quizzed on the nature of whom they are texting.
-Lying about what they are up to when asked.

Basically being a slimey slithering snake in the longgrass when it comes to trying to get with someone from the opposite sex.